This application is directed generally to a telecommunications system and in particular to a wireless telecommunications system comprised of multiple mobile switching centers (MSCs), and is more particularly directed toward conservation of paging resources and reduction of call delivery times.
In a wireline telecommunications system, such as the public switched telephone network (PSTN), the process of delivering a telephone call from a calling party to a call recipient is relatively straightforward. Since the directory number (DN) of the call recipient is provisioned to a pair of wires coupled to a central office (CO), it is simply necessary for the CO to establish a connection to the call recipient's telephone set and activate a ringing signal.
Call delivery in a wireless system, such as a cellular telephone system, is necessarily more complex. Since the specific location of a call recipient may not be well known at the time when a call is to be delivered, a cellular system attempts to locate the call recipient through a process known as paging. Since the paging process necessarily precedes every call delivery, a number of dedicated paging channels are generally reserved for this purpose.
When the cellular subscriber unit that is the designated call recipient receives a page message from a mobile switching center, the subscriber unit transmits an acknowledgement message back to the MSC, the MSC designates a voice channel for the call, and directs the subscriber unit to activate an alert signal (simulating the well-known ring of a wireline telephone set) so that call delivery can proceed.
Of course, the MSC may not know precisely where to begin its search for the call recipient. Because of this uncertainty, protocols have been established for multiple page attempts in an effort to locate the call recipient. These multiple pages occupy valuable paging channel bandwidth and extend the time required for call set-up.